The recent collapse of a major freeway bridge in Washington State has raised concerns about U.S. infrastructure—and with good reason. According to a 2011 report from Transportation for America (the latest of its kind), nearly 70,000 of the nation’s bridges are considered “structurally deficient.” That means that one or more of their crucial components—the deck, where cars, trucks and people cross; the superstructure, which supports the deck; and the substructure, which supports the superstructure from the group—has received a rating lower than four from the Federal Highway Administration, on a scale of zero to nine. They’re technically still safe to drive across, but need to be monitored closely. (The Washington bridge was actually classified as “functionally obsolete,” a level better than “structurally deficient.”) Here, a sampling of those risky bridges, ranked by average daily traffic.